Active pixel sensors are well known in the art. A typical active pixel sensor is described in U.S. Pat. No. 5,471,515.
One popular architecture for an active pixel sensor uses column-parallel A to D converters. Each A to D converter is associated with one or multiple columns. It may be desireable to associate the A to D converter with multiple columns to allow a wider pitch for its physical layout. This possibly allows more options in layout.